Johnson died over the weekend while under supervision at the facility. An autopsy conducted at the medical examiner’s office indicated Johnson died after a broken neck caused a blood clot to form in his leg, then traveled to his lung, killing him.

“What started out as a death investigation, although it’s still a death investigation at this point, but people’s necks don’t just break because they are walking down the street,” Clarke said.

Clarke said Johnson was initially admitted to the facility after Milwaukee police officers were dispatched to a home because the 25-year-old was acting irrationally.

Officers took Johnson into custody and placed him in handcuffs. He was transported to the Mental Health Complex in cuffs and leg irons; he died several days later.

Clarke would not comment on specifics of the investigation, but said authorities are looking into every detail surrounding how he was transported to the facility and what happened inside the complex.

“We’ve conducted a number of interviews of people at the facility, and I don’t want to get into at this point, but some of what we learned, some of it would raise eyebrows,” he said.

Clarke has already contacted the district attorney to provide guidance in this investigation, in case authorities discover a crime was committed in Johnson’s death.

Johnson’s family referred WISN 12 News to their attorney, Jonathan Safran, who declined to comment because the investigation is ongoing.

But at a packed memorial service at the New Restoration Christian Church, family members said they're devastated and angry about the loss of their loved one.

"He was like my little brother. When he was born, I was 8 years old, so I didn't have any younger siblings besides him being my nephew," aunt Kamesha Johnson Taylor said. "He was definitely like a little brother. He was more than just a nephew."

Taylor said Johnson was the oldest of five boys and was working on putting his business degree toward starting his own company before his life was cut short.

"He was bright. He was brilliant. He was well-rounded, very ambitious. He was just sweet. He always wanted to help people. He was about family and about love," Taylor said.

Johnson’s death is the fifth in 2012 at the Mental Health Complex. The facility did not respond to a request for comment by news time.